protected (C# Reference)
The protected keyword is a member access modifier. A protected member is accessible within its class and by derived classes. For a comparison of protected with the other access modifiers, see Accessibility Levels.
A protected member of a base class is accessible in a derived class only if the access takes place through the derived class type. For example, consider the following code segment:
// protected_keyword.cs
using System;
class A
{
protected int x = 123;
}
class B : A
{
static void Main()
{
A a = new A();
B b = new B();
// Error CS1540, because x can only be accessed by
// classes derived from A.
// a.x = 10;
// OK, because this class derives from A.
b.x = 10;
}
}
The statement a.x =10 generates an error because A is not derived from B.
Struct members cannot be protected because the struct cannot be inherited.
Example
In this example, the class DerivedPoint is derived from Point; therefore, you can access the protected members of the base class directly from the derived class.
// protected_keyword_2.cs
using System;
class Point
{
protected int x;
protected int y;
}
class DerivedPoint: Point
{
static void Main()
{
DerivedPoint dp = new DerivedPoint();
// Direct access to protected members:
dp.x = 10;
dp.y = 15;
Console.WriteLine("x = {0}, y = {1}", dp.x, dp.y);
}
}
Output
x = 10, y = 15
Comments
If you change the access levels of x and y to private, the compiler will issue the error messages:
'Point.y' is inaccessible due to its protection level.
'Point.x' is inaccessible due to its protection level.
C# Language Specification
For more information, see the following sections in the C# Language Specification:
3.5.1 Declared Accessibility
3.5.3 Protected access for instance members
3.5.4 Accessibility constraints
10.2.3 Access Modifiers
See Also
Reference
C# Keywords
Access Modifiers (C# Reference)
Accessibility Levels (C# Reference)
Modifiers (C# Reference)
public (C# Reference)
private (C# Reference)
internal (C# Reference)